And the Winner is...
There is quite a lot of data to discuss before drawing any conclusions. Let's first check out how the Radeon R9 Fury X Crossfire cards compared to the GeForce GTX 980 Ti SLI cards without any overclocking.
The average frame rate data saw the Fury X cards come out 4% ahead of the GTX 980 Tis based on the 10 games that we tested at 4K. However, of the games we tested, the Fury X combo was faster in only four of them and that includes a 1% advantage in Battlefield 4.
Where the Fury X Crossfire setup won big was in Thief where it was 50% faster and Total War: Attila where it was 36% faster. Removing Thief's result sees the Fury X cards losing to the GTX 980 Tis overall by 1%.
The games where the margin was 5% or less either way included Metro: Redux, Battlefield 4, Hitman: Absolution (due to a CPU limitation) and The Witcher 3: Wild Hunt.
Now for the interesting part, typically we expect Nvidia to have the edge when looking at frame time (99th percentile) performance, but this wasn't the case here. The R9 Fury X Crossfire cards were on average 22% faster when comparing the 99th percentile data.
Again, the Fury X Crossfire cards scored big in Thief and Total War: Attila, but were also faster in Battlefield 4, The Witcher and even Metro Redux. There was only one game where the margins were close either way and that was Hitman, again a game that we suspect was CPU limited.
The frame time wins were 50/50, but where AMD was faster it was a lot faster.
Everything changes when overclocking comes into play. The GTX 980 Ti offers loads of overclocking headroom where as the Radeon R9 Fury X offers almost none.
As a result, when comparing average frame rates once overclocked, the GTX 980 Ti graphics cards became 11% faster on average. Games where the GTX 980 Ti SLI cards were previously slower, such as Battlefield 4 and Watch Dogs, now favored the green team.
That isn't entirely surprising as overclocking saw SLI performance boosted by 15% on average, whereas the Crossfire configuration gained just a percent or two. The frame time data now also favored Nvidia by 5%.
When it comes to power consumption there were times when the R9 Fury X Crossfire system consumed over 700 watts whereas the GTX 980 Ti SLI setup never broke 600 watts, at least before any overclocking took place. That said, even when heavily overclocked, the GTX 980 Ti SLI cards still consumed considerably less than the Fury X Crossfire cards.
If we go back and look at the average frame rate performance of each game while also taking note of the minimum frame rates we see that the GTX 980 Ti SLI setup delivered very playable performance in seven of the 10 games, the Fury X Crossfire cards on the other hand provided what we consider to be very playable performance in six of the 10 games while remaining playable in the rest.
Gamers wanting to play at 4K will be happy with either setup overall, but we feel Nvidia offers a more consistent gaming experience while allowing for an additional 15% performance bump through overclocking. Normally we don't place so much emphasis on overclocking, but we feel those seeking an enthusiast multi-GPU setup are probably able and willing to enjoy the benefits of overclocking.
We'd like to thank Gainward for providing its GTX 980 Ti graphics cards for this article. The GTX 980 Ti Phoenix "GS" proved to be a strong and reliable overclocker, remaining relatively cool and almost silent under gaming load – even when the core frequency hit 1349MHz via Boost.